Sample vaporizer for gas chromatography

ABSTRACT

A heated metal block has an L-shaped bore therein, into the corner of which extends a non-wettable tube which carries the liquid sample (drop) to be vaporized from a liquid sample valve. The drop exiting from the lower open end of the tube is instantaneously vaporized, and the carrier gas or eluting gas carries the vaporized sample out of the bore and toward a chromatographic column.

United States Patent 1191 Fingerle June 17, 1975 [54] SAMPLE VAPORIZER FOR GAS 2.972.888 2/1961 Lamkin 73/231 CHROMATOGRAPHY 3,102,512 9/1963 Broerman 122/39 3,366,149 1/1968 Taft et al. 23/232 C [75] Inventor: Alfred A. Fingerle, Newtown S P quare a Primary ExaminerSi Clement Swisher 1 1 Asslgnee? Oil Q l y Pennsylvania, Attorney, Agent, or Firm-George L. Church; Donald Phlla lph R. Johnson; Frank A. Rechif [22] Filed: June 5, 1974 [21] Appl. N0.: 476,626 [57] ABSTRACT A heated metal block has an L-shaped bore therein, 1 1 Us Cl 73/422 23/253 into the corner of which extends a non-wettable tube /273 which carries the liquid sample (drop) to be vaporized [51] Int. Cl. GOln 1/00 f a li uid m le valve. The drop exiting from the of Search 0C, lower open end of the tube is instantaneously vapor- 23/230 232 253 219/273 ized, and the carrier gas or eluting gas carries the vaporized sample out of the bore and toward a chro- {561 kefereme Clled matographic column.

UNITED STATES PATENTS 2,809,100 10/1957 Krasl 23 253 Clams 2 Drawmg F'gures 4 came/5? 645 1 5mm; 5 nor- To 024w SAMPLE VAPORIZER FOR GAS CHROMATOGRAPHY This invention relates to gas chromatography, and particularly to an apparatus used for introducing samples from a liquid stream into a gas chromatography column. More particularly, the invention pertains to a device for delivering a reproducible calibrated volume of a liquid sample into a carrier gas stream wherein the liquid is flash vaporized and flushed by the carrier gas stream into a gas chromatographic apparatus.

Automatic transfer of a sample directly from a liquid process stream into a gas chromatography column presents many problems, among which is achievement of flash vaporization of the liquid sample. The major problems associated with automatic sampling of process streams of high boiling materials in the past have been the transfer of a reproducible precise sample from a liquid process stream which is maintained at a temperature from ambient up to about 80C. into a zone for flash vaporization which requires temperatures of over 300C. and thence into the gas chromatography column. Some prior devices have attempted to sample at higher temperatures, but this required maintaining the samples under high pressure to retain the samples in a liquid state for precise metering and transporting to the vaporization zone.

Transporting the metered liquid sample to the point where it is to be vaporized is a fundamental problem in process chromatography. What is required here is the transportation of the liquid sample (drop) as liquid (without any pre-vaporization) to a precise evaporation point, followed by the instantaneous evaporation (flash vaporization) of the small-volume liquid sample. The vaporized sample is of course swept by the carrier gas (eluting gas) from the evaporation point or point of vaporization to the chromatographic column.

An object of this invention is to provide a novel liquid sample vaporizer for gas chromatography.

Another object is to provide novel apparatus for the flash vaporization of a liquid sample.

A further object is to provide novel apparatus for the transfer of a calibrated volume from a liquid process stream to a position in a carrier gas stream wherein the liquid is flash vaporized and flushed by the carrier gas stream into a gas chromatography column.

A still further object is to provide novel apparatus satisfactory for precise automatic sampling of a liquid process stream containing high boiling and reactive materials, flash vaporization of the sample, and flushing such vaporized sample into a gas chromatographic apparatus.

Further details and advantages of this invention will be described in connection with the accompanying drawing illustrating a preferred embodiment of this invention, and wherein:

H0. 1 is a sectional elevation illustrating the preferred embodiment of this invention; and

FIG. 2 is a cross-section taken along line 22 of FIG. 1, and drawn on an enlarged scale.

Turning now to the drawings, there is shown in sectional elevation the inventive device for introducing volatile samples into a conduit 1 containing eluting gas passing through a heat-conducting metal block 2. The block 2 is suitably a single block of a metal which has a relatively high heat transfer rate, such as brass or a stainless steel. Several conduits and bores are drilled therein to provide a conduit or bore 1 for the eluting gas, a hole 3 to accommodate an electrical bayonet or cartridge heater 4, and in addition one or more holes (not shown) for the purpose of receiving thermocouples. During operation, the heater 4 is powered from an electrical source by means of the leads 5 to heat the block 2 to an elevated temperature, on the order of 300C.

Eluting or carrier gas conduit 1 is drilled in two directions, one 1a being vertical and the other 1b being horizontal, thereby to form an L-shaped combined or composite bore. The vertical portion la is threaded at its upper or inlet end 6 to receive one end of a tee fitting 7 (to be later referred to), while the horizontal portion lb is threaded at its outlet end 8 l/l6-inch diameter) to receive an outlet conduit which leads to a gas chromatography column of conventional type.

As previously stated, one end of the tee 7 is threaded into block 2. Carrier or eluting gas is admitted through the tee portion 9 and passes into bore or conduit 1 via the lower portion 10 of the fitting 7. The upper portion 11 of tee 7, which is in vertical alignment with tee portion 10 and block inlet 6, extends upwardly and has sealed therein, by means of a conventional threaded fitting and ferrule 12, a length of stainless steel tubing 13, e.g. of /a inch O.D. Preferably, the lower end of tube 13 extends downwardly beyond the ferrule 12, as illustrated, terminating near the lower end of the lower portion 10 of tee 7.

Tube 13 preferably extends vertically upwardly from fitting 7, as illustrated, and the upper end of this tube is suitably secured to a liquid sample valve of known type, represented by the block 14.

The liquid sample valve 14 may, for example, be of the type disclosed in Pat. No. 3,122,l68, or in Pat. No. 3,223,123.

As is usual in the art of gas chromatography, small samples of liquids are utilized, usually 0.0001 to 1.0 milliliter (0.1 to 1000 microliters). By way of example, a liquid sample drop of four microliters will be referred to herein. According to known practice, and as disclosed in the abovementioned patents, carrier gas is used to sweep the sample out of the sampling valve 14 toward the chromatograph. This gas is fed at a low flow rate into valve 14 by means of a connection 15.

The sample is fed into valve 14 by means of a connection or conduit 18, and the sample, when not being swept to the chromatograph, is bypassed to a drain by means of the connection or conduit 19.

According to this invention, the liquid sample is swept out of the sampling valve 14 into a sample vaporizer, on its way to the chromatograph. This sample travels through a tube made of an oleophobic, hydrophobic, non-wettable and heat insulating material, on its way from the sampling valve 14 to the vaporization point in block 2, which point is located at the corner of the L-shaped bore 1.

Fitting snugly inside the tube 13 is a length of tubing 16, the CD. of which is substantially equal to the ID. of the stainless steel tubing 13. The tubing 16 is preferably made of a Teflon polymer, which has the characteristics set forth in the preceding paragraph that is to say, it is oleophobic, hydrophobic, non-wettable, and heat insulating, and in addition, it has self-lubricating characteristics. The stainless steel tubing 13, in addition to providing an enhanced seal at fitting 7 (ferrule 12), serves to support the tubing 16 (since tubing 13 is very rigid as compared to tubing 16).

Tube 16 extends substantially vertically. The upper end of this tube is sealingly coupled to the Sample Out connection provided in sampling valve 14. Tube 16 extends down through tube 13 and tee fitting 7, beyond the lower end of the open-ended tube 13, the lower open end of tube 16 being located closely adjacent the corner of bore 1, that is, closely adjacent the junction of bore portions la and lb.

During operation, carrier gas is admitted through the tee portion 9 of tee 7, this gas flowing downwardly through the lower portion 10 of this fitting (around the outside of tube 13), thence through bore portion la (around the outside of tube 16), and thence through bore portion lb and out of the block 2, to the chromatographic column. Carrier gas is also fed into valve 14 through connection 15. The block 2 is heated to an elevated temperature by means of heater 4.

The sampling valve 14 operates in a well-known manner to produce a small-volume liquid sample (for example, a drop of about 4 microliters in size), illustrated at 17 in FIG. I. This drop, exiting from the valve 14, travels through the non-wettable tube 16 to the lower end thereof (i.e., to the evaporation point at the corner of the L-shaped bore 1). Since the sample drop does not wet the tube 16, there is no loss of liquid and no prevaporization, so the precise quantity of liquid sample leaving valve 14 reaches the evaporation point (corner of bore 1).

The drop 17 of liquid, thus transported to the evaporation point, leaves the lower open end of tube 16 and comes into contact with the heated surface of the block (wall of bore 1), where it is instantaneously vaporized or evaporated. The vaporized sample is then swept or flushed by the carrier gas by way of bore portion lb, out of the block 2 to the chromatographic column.

It should be realized that, by means of the sample vaporizer of this invention, a small, very precise quantity of liquid sample (actually, a drop) is transported to a definite evaporation point and is then instantaneously vaporized, following which the vaporized sample is swept on to a chromatographic column.

Due to the use of a non-wettable material for the tube 16, the sample size is exactly the same for each operation. That is to say, the repeatability is excellent, which is very important in chromatography, utilizing as it does sequential or successive sampling operations.

The invention claimed is:

1. An apparatus for introducing a small sample of a volatile liquid into a chromatographic carrier gas stream which comprises: a block of heat-conducting metal, said block having a continuous carrier-gas transmitting conduit extending through the interior thereof with an inlet end and an outlet end both opening into the outer surface of the block; heater means for heating said block to an elevated temperature with respect to the ambient, a sample-liquid transmitting conduit of oleophobic material extending through said conduit inlet end into communication with said continuous conduit at a point in the interior of said block, and means providing for connection of said conduit outlet end to a chromatographic column.

2. Apparatus according to claim 1, wherein said liquid transmitting conduit comprises a tube made from a material which is non-wettable by an oleaginous liquid.

3. Apparatus set forth in claim 2, wherein said mate rial is a Teflon resin.

4. Apparatus set forth in claim I, wherein said continuous conduit is substantially L-shaped, and wherein said liquid transmitting conduit communicates with said L-shaped conduit at a point immediately adjacent the corner thereof.

5. Apparatus set forth in claim 1, wherein said liquid transmitting conduit extends from a liquid sample valve to said point of communication; said apparatus including also a rigid tube closely surrounding a substantial portion of the length of said liquid transmitting conduit to provide mechanical support for such conduit.

6. Apparatus of claim 1, including also means for feeding carrier gas into the inlet end of said continuous conduit.

7. Apparatus set forth in claim 6, wherein said continuous conduit is substantially L-shaped, and wherein said liquid transmitting conduit communicates with said L-shaped conduit at a point immediately adjacent the corner thereof.

8. Apparatus according to claim 7, wherein said liquid transmitting conduit comprises a tube made from a material which is non-wettable by an oleaginous liquid.

9. Apparatus set forth in claim 8, wherein said material is a Teflon resin.

10. Apparatus set forth in claim 8, wherein said liquid transmitting conduit extends from a liquid sample valve to said point of communication; said apparatus including also a rigid tube closely surrounding a substantial portion of the length of said liquid transmitting conduit to provide mechanical support for such conduit. 

1. An apparatus for introducing a small sample of a volatile liquid into a chromatographic carrier gas stream which comprises: a block of heat-conducting metal, said block having a continuous carrier-gas transmitting conduit extending through the interior thereof with an inlet end and an outlet end both opening into the outer surface of the block; heater means for heating said block to an elevated temperature with respect to the ambient, a sampleliquid transmitting conduit of oleophobic material extending through said conduit inlet end into communication with said continuous conduit at a point in the interior of said block, and means providing for connection of said conduit outlet end to a chromatographic column.
 2. Apparatus according to claim 1, wherein said liquid transmitting conduit comprises a tube made from a material which is non-wettable by an oleaginous liquid.
 3. Apparatus set forth in claim 2, wherein said material is a Teflon resin.
 4. Apparatus set forth in claim 1, wherein said continuous conduit is substantially L-shaped, and wherein said liquid transmitting conduit communicates with said L-shaped conduit at a point immediately adjacent the corner thereof.
 5. Apparatus set forth in claim 1, wherein said liquid transmitting conduit extends from a liquid sample valve to said point of communication; said apparatus including also a rigid tube closely surrounding a substantial portion of the length of said liquid transmitting conduit to provide mechanical support for such conduit.
 6. Apparatus of claim 1, including also means for Feeding carrier gas into the inlet end of said continuous conduit.
 7. Apparatus set forth in claim 6, wherein said continuous conduit is substantially L-shaped, and wherein said liquid transmitting conduit communicates with said L-shaped conduit at a point immediately adjacent the corner thereof.
 8. Apparatus according to claim 7, wherein said liquid transmitting conduit comprises a tube made from a material which is non-wettable by an oleaginous liquid.
 9. Apparatus set forth in claim 8, wherein said material is a Teflon resin.
 10. Apparatus set forth in claim 8, wherein said liquid transmitting conduit extends from a liquid sample valve to said point of communication; said apparatus including also a rigid tube closely surrounding a substantial portion of the length of said liquid transmitting conduit to provide mechanical support for such conduit. 